The invention relates to coiled tubing injectors, and apparatus and methods for combining conventional sectional tubing drilling with drilling using coiled tubing. More particularly, a collapsible mast and a rotary table can be arranged for operation with both a catwalk for sectional tubulars and with a coiled tubing unit. A linear coiled tubing injector is sufficiently narrow to coexist in the mast while tripping conventional tubulars.
The general background relating to coiled tubing injector units is described in U.S. Pat. Nos. 5,839,514 and 4,673,035 to Gipson which are incorporated herein by reference for all purposes.
Apparatus for conventional drilling with sectional tubing is very well known.
Coiled tubing has been a useful apparatus in oil field operations due to the speed at which a tool can be run in (injected) and tripped out (withdrawn) from a well bore. Coiled tubing is supplied on a spool. An injector at the wellhead is used to grip and control the tubing for controlled injection and withdrawal at the well. As coil tubing cannot be rotated, drilling with coiled tubing is accomplished with downhole motors driven by fluid pumped downhole from the surface.
The use of coiled tubing has advantages over conventional drilling due to the potential to significantly speed drilling and reduce drilling costs through the use of continuous tubing. The most significant cost saving factors include the reduced pipe handling time, reduced pipe joint makeup time, and reduced leakage risks.
Exclusive use of coiled tubing is associated with several limitations. Certain stages of drilling operations still require making up of threaded joints, the means for which are not typically provided with coiled tubing rigs. Further, a coiled tubing injector has limited pulling strength as compared to the draw works provided with conventional sectional tubing masts. Further, a conventional wellhead injector tends to inject tubing which has a residual bend therein. Residual bend results in added contact and unnecessary forces on the walls of the drilled hole or casing, increasing frictional drag and causing an offset positioning of the tubing within the hole. Occasionally the coiled tubing can wad up in the hole (like pushing a resilient rope through a tube) and cannot be injected any further downhole or ever actually reach total depth.
As described in U.S. Pat. No. 5,842,530 to Smith et al. (Smith), apparatus is disclosed which is directed to providing a single rig having both conventional and coiled tubing capability. Smith describes how sectional tubing is used during the vertical, and substantially linear, drilling and switching to non-rotation tubing and downhole motors after deviating the well to the horizontal. However, by combining the two technologies in a single rig, Smith""s mast is limited in its crown and draw works capacity. Further, Smith discloses the use of a conventional injector.
A conventional injector comprises two continuous, parallel and opposing conveyors having grooved shoes or blocks mounted thereon such as that disclosed in U.S. Pat. No. 5,533,668 to Council et al. for Halliburton Company, Oklahoma. The opposing conveyors have facing portions where the multiplicity of gripping blocks run parallel for gripping the tubing therebetween, typically positioned inline, directly adjacent and above the wellhead.
One characteristic of the dual conveyor injectors is that the facing grooved blocks must have absolutely synchronous timing and engagement with the coiled tubing, the failure to do so being associated with damage to the coiled tubing. Damage to the coiled tubing further reduces the lifespan of tubing already suffering a short lifespan due to reversing stresses inherent in the technique.
In U.S. Pat. No. 5,839,514 to Gipson, an improved injector comprises a grooved reel and hold-down rollers for imparting the gripping force necessary to drive the coiled tubing. This reel type injector, while causing less damage to the tubing than the block type is limited in pull capability, in part due to the short tubing gripping length. The gripping length of reel-type coiled tubing drives is limited by the circumference of the reel; the maximum circumference being limited to less than 360 degrees due to the inability to permit overlap tubing wrapped around a grooved driving reel.
Deeper wells can be accessed, for either workover or drilling purposes if the pull strength can be increased. Further, deeper wells usually require larger diameter tubing to handle greater string weight and to minimize fluid pumping power requirements. As the fluid for driving mud motors is delivered down the bore of tubing, fluid friction causes significant pressure drop and thus requires large power sources at the pumps. The larger the tubing, the lower the fluid friction losses and the lower the power requirements.
Rigs utilizing either the dual conveyor or the reel type injectors have had difficulty in dealing with larger diameter tubing. Further, while the use of coiled tubing has enabled faster operation to depth and out again, the equipment has a higher capital and operating cost. For example, coiled tubing rigs use more complicated and expensive equipment, have higher power requirements for overcoming fluid friction losses and the repeatedly deformed coiled tubing has a limited life which requires periodic replacement with new coiled tubing.
Further, coiled tubing apparatus is typically provided on a single transportable rig which provides a spool of coiled tubing, an injector and its own mast which is designed for light or small diameter coiled tubing, portability and generally low pull weight. In summary, the mast and rigs generally are not suitable for work with deeper wells.
Linear Injector
In one aspect the linear injector of the present invention extends coiled tubing capability beyond that known heretofore. In combination with a conventional jointed drilling rig, none of the functionality of the conventional rig is sacrificed while achieving enhanced capabilities by the addition of coiled tubing.
In the preferred embodiment, coiled tubing is driven along a linear section of an endless chain conveyor with an opposing linear array of rollers. Using prior art dual conveyors, gripper blocks pull on both sides of the coiled tubing and the present invention only pulls on one side. Applicant has found that by eliminating the prior art parallel chain drives, the difficulty to synchronize the two drives is avoided and the substitution of non-driving rollers for one side of the tubing injector results in less damage to the coiled tubing. Further, by eliminating the challenge of maintaining dual chain synchronicity, the novel injector is able to take unrestricted advantage of an extended length of a linear driving section, thus providing superior injection and pulling capability.
Accordingly, in one preferred aspect of the invention, deep wells can be drilled with coiled tubing even from the surface due to the combination of enabling the use of full diameter tubing, implementing a straightener and using an injector which is capable of applying both significant injector force on a drilling bit and full pulling capability for tripping out of the deep wells. An injector of 20 feet in length is capable of a nominal pulling capacity of about 100,000 lb. force. Further, suspension of the preferred injector in a conventional derrick having strong draw works and a rotary table permits operation with both conventional sectional tubing, including BHA, and simplifying the making up to coiled tubing.
In a broad aspect of the invention then, coiled tubing injection apparatus is provided comprising:
a chain conveyor extending about an endless path and having at least one linear section aligned with the wellbore;
a multiplicity of gripper blocks conveyed and driven by the chain conveyor, the gripper blocks forming a substantially continuous coiled tubing support while traversing the linear portion;
a linear array of a multiplicity of rollers in parallel and opposing arrangement to the linear section of the chain conveyor for forming a corridor therebetween and through which the coiled tubing extends, the rollers urging the coiled tubing into frictional engagement with the gripper blocks;
means for supporting the gripper blocks against the normal forces produced by the linear array of rollers; and
means for driving the chain conveyor along the endless path so as to drive the gripper blocks which frictionally drive the coiled tubing along the corridor.
Preferably idlers extend laterally from the gripper blocks for rolling along a track, thereby supporting the normal forces on the chain conveyor. More preferably, biasing means are provided for adjusting the normal force imposed by the rollers against the coiled tubing. Further, a tubing straightener is positioned between the apparatus and a source of coiled tubing, just preceding the corridor between the linear portion of the gripper blocks and the linear array of rollers.
In another embodiment, the linear injector can be pivotally mounted to a mobile transport for aligning the linear injector with wellheads at any angle to the surface.
In another aspect, the present invention utilizes a combination of apparatus which borrows the best of both the conventional and coiled tubing drilling apparatus for providing improved efficiency in drilling operations. Both the conventional and coiled tubing art is improved to permit even deep wells to be drilled using coiled tubing. While conventional coiled tubing injectors could be used, they must be narrow enough to standby in the mast while sectional drilling is ongoing. One such injector is a novel coiled tubing linear injector which further extends coiled tubing capability beyond that known heretofore. When used in combination with a mast capable of handling conventional tubing, none of the functionality of the conventional rig is sacrificed while achieving enhanced capabilities by the addition of coiled tubing. Where it would normally be required to use a very tall mast for making up stands of sectional pipe, a shorter mast can be implemented with coiled tubing. Further, by providing a mast which is accessible on two sides, and having a side-shifting crown assembly with dual block/hooks combinations, then operations with both conventional sectional and coiled tubing is radically simplified and streamlined.
In a preferred embodiment, two rigs are provided. A first rig comprises a collapsible mast on a trailer, a substructure, rotary tubing drive means (table or power swivel), side shifting crown, dual blocks and dual drawworks. An integrated hydraulic system powers the drawworks, side-shifting crown, rotary table and lifts the collapsible mast. A second rig comprises a coiled tubing injector and a reel of coiled tubing on a trailer. Suitable support equipment is provided such as a mud system, mud pump and control house. The two rigs are arranged tail to tail. The mast, when erected, has a first side open to the deck of the trailer of the first rig, forming a catwalk for drill pipe. The opposing side of the mast is open to the second coiled tubing rig. Accordingly, lengths of sectional tubulars can be handled or drawn up the first open side from the first rig; and coiled tubing can be introduced from the second side.
While other injectors of mast-capable installation are anticipated, in the most preferred embodiment, the novel injector meets all the requirements, having a shallow depth and can idle, set aside in the mast, when handling sectional tubulars (tubing or casing). Simply, the preferred injector comprises a linear section of an endless chain conveyor with an opposing linear array of tubing holddown rollers. As disclosed above, by eliminating the prior art dual and parallel chain drives it is possible to eliminate the known difficulty of synchronizing the two drives and to avoid the bulky machinery of dual chain drives required to hold the dual drives in facing relation. Further, the substitution of non-driving rollers for one side of the tubing injector results in less damage to the coiled tubing. Further, by eliminating the challenge of maintaining dual chain synchronicity, the novel injector is able to take unrestricted advantage of an extended length of a linear driving section, thus providing superior injection and pulling capability and enabling use of conventional diameter tubing.
Accordingly, in one preferred aspect of the invention, deep wells can now be drilled with coiled tubing, even from the surface, due to the implementation of an injector which is capable of applying both significant injector force on a drilling bit and full pulling capability for tripping out of the deep wells, and preferably a straightener and even being able to using conventional diameters of sectional tubulars. It is noted that the novel injector of 15 feet in length is capable of a nominal pulling capacity of about 80,000 lb. force. Further, suspension of the preferred injector in a mast, having both strong draw works and a rotary table, permits operation with both conventional sectional tubing, including assembling of the BHA, and simplifying the making up to coiled tubing. Having both open sides minimizes the footprint of this hybrid drilling apparatus. Further drilling efficiency is improved, eliminating wasted steps formerly required to decommission one type of drilling apparatus and commission the other.
In a broad aspect of the invention then, a method for hybrid drilling of a well with both sectional tubulars and coiled tubing comprises the steps of:
providing a hybrid drilling system having a mast having at least one open side and equipped for drilling with tubulars, at least one drawworks and a drive for rotating tubulars, and having a coiled tubing injector having a supply of coiled tubing;
lifting the injector into the mast using the drawworks;
alternately drilling with tubulars or with coiled tubing; and
setting the injector aside in the mast when drilling with tubulars.
Preferably, the method further comprises handling tubulars and coiled tubing through the same open side of the mast. More preferably, the tubulars and are handled through separate open sides of the mast.
In a broad aspect, apparatus for achieving the above method comprises:
a mast over the well having at least one open side;
drawworks and a rotary drive for the handing and drilling of the tubulars through the mast""s open side; and
a coiled tubing injector and supply of coiled tubing, the injector being sufficiently compact to be hung in the mast from the drawworks with the coiled tubing being supplied through the mast""s open side.
Preferably the apparatus comprises a mast and tubular rotating means, the mast having a side shifting crown having at least two positions over the well and first and second opposing and open sides, a first block/hook fitted to the side shifting crown and being fitted with elevators for handling tubing through the first open side; a second block/hook being fitted to the side shifting crown, the second block hook being alternately fitted with, a swivel for rotary drilling with tubulars, and a coiled tubing injector for drilling with coiled tubing supplied through the second open side; and a coiled tubing injector, preferably one having a bi-directional driven chain fitted with tubing gripper blocks which extend about an endless path and having at least one linear supported section aligned with the wellbore, and a linear array of hold-down rollers in parallel and opposing arrangement to the linear section of the chain conveyor for forming a corridor therebetween and through which coiled tubing extends, the rollers urging the coiled tubing into frictional engagement with the gripper blocks.